The present invention relates to a liquid crystal display device, and more particularly to an IPS mode liquid crystal display device with excellent viewing angle characteristics and designed to prevent the occurrence of reverse domain.
A display device includes a TFT substrate in which pixels each having a pixel electrode, a thin film transistor (TFT), and the like are arranged in a matrix form. Further, there is provided a counter substrate opposite the TFT substrate, in which color filters and the like are formed at positions corresponding to the pixel electrodes of the TFT substrate. Further, a liquid crystal is interposed between the TFT substrate and the counter substrate. Then, an image is formed by controlling the transmittance of light through each pixel by the liquid crystal molecules.
Liquid crystal display devices are flat and lightweight and thus are used in a variety of applications. Small liquid crystal display devices are widely used in mobile phones, digital still cameras (DSC), or other portable devices. The viewing angle characteristics are a problem in the liquid crystal display device. The viewing angle characteristics are a phenomenon that the brightness changes or the chromaticity changes between when the screen is viewed from the front, and when it is viewed in an oblique direction. The viewing angle characteristics are excellent in the In Plane Switching (IPS) mode for driving liquid crystal molecules by an electric field in the horizontal direction.
Although the IPS mode has excellent viewing angle characteristics, there is a case where the so-called azimuthal characteristics are not uniform, in which the viewing angle characteristics vary depending on the direction of viewing the screen. In order to address such a problem, Japanese Unexamined Patent Application Publication No. 2000-56336 describes a structure in which two domains with different rotational directions of liquid crystal molecules are formed in one pixel in order to reduce the azimuthal dependence of the viewing angle. This is sometimes called the dual domain method.
Further, when the surface of the liquid crystal display panel is pushed by a finger or other things, the distance between the counter substrate and the TFT substrate changes in this portion. As a result, a domain occurs due to the fact that the liquid crystal moves. This domain is a problem if it does not disappear quickly. Japanese Unexamined Patent Application Publication No. 2000-56320 describes a structure designed to prevent the occurrence of such a push domain.